Model Of Nonlinear Electrodynamics Research Articles

Gravity and [formula omitted] flows in higher dimensions

We study systems in arbitrary space-time dimensions where matter, deformed by TT‾-like irrelevant operators, is coupled to gravity in the Palatini formalism. The dynamically equivalent perspective is investigated, wherein the deformation transitions from the matter action to the gravitational one or vice versa. This alternative viewpoint leads to the emergence of Ricci-based gravity theories, thus providing a high-dimensional generalisation of the well-known equivalence between two-dimensional TT‾ deformations and coupling to Jackiw-Teitelboim gravity. This dynamical equivalence is examined within the framework of the recently introduced Lagrangian flow equation, which notably led to the discovery of a direct link between Nambu-Goto theory and TT‾ in d=2, as well as significant insights into nonlinear electrodynamics models in d=4. The investigation involves explicit examples in d=4 dimensions; it builds upon earlier research concerning the metric interpretation of TT‾-like perturbations, incorporates and extends recent findings in the cosmology-related literature associated to the concept of reframing. We focus on scenarios where the resulting modified gravity theories manifest as Born-Infeld and Starobinsky types.

Inflation Driven by Nonlinear Electrodynamics in Anisotropic Spacetime

The well-known Big Bang theory has explained how the universe came into being. This extraordinary event caused the later universe to be accelerated by a scale factor a(t). However, standard Big Bang theory has had some problems that can’t be explained, such as monopoles, horizons, and flatness. To solve this problem, a model of inflation in the early universe is required. Recent studies show that nonlinear electrodynamics coupled with general relativity can describe the inflation of the universe. In this work, we consider a model of nonlinear electrodynamics in anisotropic spacetime. We derive the dynamical equation from Einstein’s field equation and the law of conservation of energy-momentum tensor. Then, we use the perturbation method to solve the dynamical equation of the universe and obtain the evolution of the non-singular scale factor with anisotropy parameter ϵ. Using a phase-space analysis of the inflationary model, we obtain a phase portrait in the presence of fixed points. Our result shows that in the model of nonlinear electrodynamics coupled to gravity in anisotropic spacetime, the universe can undergo an inflationary mechanism if ϵ < 1. We also show the absence of singularity in density and pressure using this model.

Analytic Electrically Charged Black Holes in F(R)-ModMax Theory

Abstract Motivated by a new model of nonlinear electrodynamics known as Modified Maxwell (ModMax) theory, an exact analytical solution for black holes is obtained by coupling ModMax nonlinear electrodynamics and F(R) gravity. Then, the effects of the system’s parameters (F(R)-ModMax gravity parameters) on the event horizons are analyzed. The obtained black hole thermodynamic properties in the F(R)-ModMax theory are investigated by extracting their thermodynamic quantities such as Hawking temperature, electric charge, electric potential, entropy, and also total mass. The first law of thermodynamics for the system under study is evaluated. Next, by considering these black holes, the impacts of various parameters on both the local stability and global stability are investigated by examining the heat capacity and the Helmholtz free energy, respectively. Finally, the thermodynamic geometry of the black hole in F(R)-ModMax gravity is investigated by applying the Hendi–Panahiyan–Eslam Panah–Momennia thermodynamic metric (HPEM’s metric).

Confinement and nonlinear electrodynamics: Asymptotic Schwarzschild charged black hole

While most nonlinear electrodynamics (NED) models tend to Maxwell’s linear theory in the weak field regime, very recently a model of NED has been proposed in the context of heavy quark–antiquark confinement that gives the same limit in the strong field regime. This form of correction to Maxwell’s linear theory is shown to be applicable in such a confined system. In this model, the radial electric field of a point charge is described by E=qr2+ζqr which consists of a Coulomb term plus a term proportional to the NED parameter ζ. Here in this paper, we extend the previous study on the model and accordingly, first, present more on the properties of the model and then introduce the magnetic black hole solution obtained in the gravity coupled minimally to this NED. The solution due to the unique property of the NED is asymptotically Schwarzschild black hole. In addition to the thermodynamics of the black hole, we investigate the circular speed–radius curve of the hypothetical star orbiting the mentioned black hole. It is shown that again due to the correction of Maxwell’s theory in the weak field limit these curves are equivalent to the corresponding curves in the Schwarzschild black hole.

Quark-antiquark confinement and nonlinear electrodynamics

Cornell potential is known to represent the quark-antiquark confinement interaction. In addition to the Cornell potential, there have been other interactions in the literature that demonstrate confining structure in the quark-antiquark system. Guendelman has proposed a nonlinear electrodynamics (NED) model which results in electric potential in the form of Cornell interaction. In this study, we propose two NED models whose electric potential is in the form of two other confining potentials. We also study the coupling of gravity to one of these models which are in the form of a correction to linear Maxwell's theory. We find spacetime which can be a black hole or a naked singular particle. In the zeroth approximation, we examine the circular speed of a distant test particle orbiting the central black hole. The Newtonian potential due to the spacetime at the location of the distant particle possesses an additional term proportional to the NED parameter. Due to the presence of such a term, the speed-radius curve gets improved from the pure Reissner-Nordstrom. It is a kind of weaker confinement acting on distant parts of a galaxy due to a supermassive central black hole.

Dyonic matter equations, exact point-source solutions, and charged black holes in generalized Born-Infeld theory

We derive the equations of motion governing static dyonic matters, described in terms of two real scalar fields, in nonlinear electrodynamics of the Born--Infeld theory type. We then obtain exact finite-energy solutions of these equations in the quadratic and logarithmic nonlinearity cases subject to dyonic point-charge sources and construct dyonically charged black holes with relegated curvature singularities. In the case of quadratic nonlinearity, which is the core model of this work, we show that dyonic solutions enable us to restore electromagnetic symmetry, which is known to be broken in non-dyonic situations by exclusion of monopoles. We further demonstrate that in the context of k-essence cosmology the nonlinear electrodynamics models possess their own distinctive signatures in light of the underlying equations of state of the cosmic fluids they represent. In this context, the quadratic and logarithmic models are shown to resolve a density-pressure inconsistency issue exhibited by the original Born--Infeld model k-essence action function as well as by all of its fractional-powered extensions. Moreover, it is shown that the quadratic model is uniquely positioned to give rise to a radiation-dominated era in the early universe among all the polynomial models and other examples considered.

Emergent cosmology in models of nonlinear electrodynamics

Nonlinear electrodynamics, which acts as a source of gravity Einstein field equations, leads to emergent cosmology, an alternative solution which can avoid Big Bang singularity. In this paper, we explore the emerging universe in models of non-linear electrodynamics (described by dimensional parameter β) by using the equation of state parameter ω and see how the parameter β helps the universe to cause a transition from a quasi-static Minkowski phase to the inflationary phase of expansion through the point of emergence and subsequently to the phase of normal thermal expansion. We predict the spectral index parameter ns=0.97467 (scalar spectral index), r=0.10133 (tensor to scalar ratio) and nT=−0.01267 (tensor spectral index) of the inflationary perturbation in emergent cosmology of nonlinear electrodynamics corresponding to β= 0.1 and B0=10−10 G.

Generalization of the Guendelman nonlinear electrodynamics model

In this study, we present a generalized version of the specific nonlinear electrodynamic model introduced by Guendelman [PLB640(2006)201] as a result of spontaneously breaking the scale invariance of Maxwell’s linear theory. The generalized model involves a new integer parameter n so that n = 2 reproduces Guendelman’s model. Although with each n in principle there exist a new model but technically only n = 2 and n = 3 yield a closed analytical expression.

Cylindrically symmetric self-sustaining solutions in some models of nonlinear electrodynamics

In this article, we discuss the extension of the Melvin solution for the geon to some models of non-linear electrodynamics with the exact form of the Lagrangian, in particular, for a conformally invariant model (CNED), whose Lagrangian depends on the second and fourth order invariants of the electromagnetic field tensor.

Charged black holes from a family of Born–Infeld-type electrodynamics models

We present a family of nonlinear electrodynamics models that are free of the infinite self-energy of the point charge. Each model is dependent on a dimensional nonlinearity parameter and is determined by the integer value of a dimensionless parameter [Formula: see text]. The Born–Infeld model is recovered when [Formula: see text]. Some of the characteristics of this family are studied. In addition, we study the solutions of electrically charged AdS black holes, which result from coupling these electrodynamic models to General Relativity. A Smarr formula consistent with the first law of thermodynamics is also obtained in an extended phase space.

Lovelock black holes with double-logarithmic electrodynamics source

This work examines the magnetized black holes of Lovelock gravity in the presence of double-logarithmic electrodynamics. In this context, the Lovelock polynomial is found and the accompanying thermodynamic quantities, such as mass, entropy, Hawking temperature, and heat capacity, are determined. This new model of nonlinear electrodynamics is used to calculate the black hole solutions of Einstein, Gauss–Bonnet and third-order Lovelock gravities as well. The impacts of the double-logarithmic electromagnetic field on the black hole thermodynamics in these particular theories are examined and the regions of horizon radius that correspond to the local thermodynamic stability are highlighted.

Novel traversable wormhole in general relativity and Einstein-Scalar-Gauss-Bonnet theory supported by nonlinear electrodynamics

Several traversable wormholes (T-WHs) of the Morris-Thorne type have been presented as exact solutions of Einstein-nonlinear electrodynamics gravity (GR-NLED), e.g. \cite{Arellano2009, Bronnikov2018,Bronnikov_Walia2021, Canate_Breton2018, Canate_Breton_Ortiz2020, Canate_Magos_Breton2020}. However, none of these solutions is support by a nonlinear electrodynamics model satisfying plausible conditions. In this work, we present the first traversable wormhole solution of Einstein-nonlinear electrodynamics gravity coupled to a self-interacting phantom scalar field (GR-NLED-SF) with a NLED model such that in the limit of weak field becomes the Maxwell electrodynamics, is presented. Furthermore, we show that this novel T-WH spacetime is also an exact solution of the Einstein-scalar-Gauss-Bonnet (EsGB) theory with a nonlinear electrodynamics source, but now with a real scalar field having a positive kinetic term.

Regular black hole powered by a self-gravitating magnetic monopole

We apply the formalism introduced in (2022 S. H. Mazharimousavi, Eur. Phys. J. Plus 137, 595) to present a two parameters regular static spherically symmetric black hole that is asymptotically Reissner-Nordström. Also, the near r = 0 behavior of the model is a de-Sitter regular spacetime. A self-gravitating magnetic monopole powers it. The energy-momentum tensor of the black hole satisfies the weak energy condition. The black hole is thermally stable when the event horizon’s radius is close to the extremal black hole. We also show that this regular black hole is an exact solution to the field equations in the gravity coupled with a new model of nonlinear electrodynamics.

ModMax model of nonlinear electrodynamics without the linear term

The ModMax model of nonlinear electrodynamics (NED) is investigated in the absence of the linear term. The linear term is itself a ModMax model, however, the nonlinear term is not. First, in (3+1)-dimensional Minkowski spacetime, we introduce the electromagnetic theory in this NED model. We find the vacuum electric permittivity and magnetic permeability which both are in tensor form. This shows that the propagation of the speed of the electromagnetic wave depends on the direction. Finally, we couple our NED Lagrangian density minimally with the standard gravity and find a dyonic black hole solution.

Maximally symmetric nonlinear extension of electrodynamics and charged particles

We consider couplings of electrically and magnetically charged sources to the maximally symmetric non-linear extension of Maxwell's theory called ModMax. The aim is to reveal physical effects which distinguish ModMax from Maxwell's electrodynamics. We find that, in contrast to generic models of non-linear electrodynamics, Lienard-Wiechert fields induced by a moving electric or magnetic particle, or a dyon are exact solutions of the ModMax equations of motion. We then study whether and how ModMax non-linearity affects properties of electromagnetic interactions of charged objects, in particular the Lorentz force, the Coulomb law, the Lienard-Wiechert fields, Dirac's and Schwinger's quantization of electric and magnetic charges, and the Compton Effect. In passing we also present an alternative form of the ModMax Lagrangian in terms of the coupling of Maxwell's theory to axion-dilaton-like auxiliary scalar fields which may be relevant for revealing the effective field theory origin of ModMax.

On charged black holes in 4D Lovelock theory coupled to ModMax nonlinear electrodynamics

The ModMax nonlinear electrodynamics is a recently proposed model which possesses maximally symmetries among the well-known nonlinear electrodynamics models. This model consists of both Maxwell’s invariants such that in the absence of either the electric or the magnetic field the model automatically reduces to the Maxwell linear theory. The presence of both scalar invariants which are necessary for the symmetries of the model makes it very special such that cannot be employed in higher or lower dimensions. Unfortunately, we observed in the literature that, this model has been applied in higher d-dimensions. This is still an early time for this model, however, it is becoming popular. We aim to clarify this specific important point by giving the correct approach to the 4D Einstein–Gauss–Bonnet gravity as well as 4D Einstein p-order Lovelock theory coupled to ModMax nonlinear electrodynamics.

Slowly rotating black holes in nonlinear electrodynamics

We show how (at least, in principle) one can construct electrically and magnetically charged slowly rotating black hole solutions coupled to nonlinear electrodynamics (NLE). Our generalized Lense--Thirring ansatz is, apart from the static metric function $f$ and the electrostatic potential $\ensuremath{\phi}$ inherited from the corresponding spherical solution, characterized by two new functions $h$ (in the metric) and $\ensuremath{\omega}$ (in the vector potential) encoding the effect of rotation. In the linear Maxwell case, the rotating solutions are completely characterized by a static solution, featuring $h=(f\ensuremath{-}1)/{r}^{2}$ and $\ensuremath{\omega}=1$. We show that when the first is imposed, the ansatz is inconsistent with any restricted (see below) NLE but the Maxwell electrodynamics. In particular, this implies that the (standard) Newman--Janis algorithm cannot be used to generate rotating solutions for any restricted nontrivial NLE. We present a few explicit examples of slowly rotating solutions in particular models of NLE, as well as briefly discuss the NLE charged Taub-NUT spacetimes.

Nonlinear Maxwell equations and strong-field electrodynamics

We investigate two Lagrangian models of nonlinear electrodynamics (NLED). These models lead to two different sets of nonlinear (NL) Maxwell equations. The first case deals with the well-known Heisenberg-Euler (HE) model of electromagnetic (EM) self-interactions in a vacuum where only the lowest orders in EM Lorentz invariants are considered. The second instance proposes an extension of the HE model. It consists of a NL Maxwell-Dirac spinor model where the EM field modifies the dynamics of the energy-momentum operator sector of the Dirac Lagrangian instead of its rest-mass term counterpart. This work complements our recent research on NL Dirac equations in the strong EM field regime.

Magnetic black holes with generalized ModMax model of nonlinear electrodynamics

Recently, Bandos, Lechner, Sorokin and Townsend [Phys. Rev. D 102 (2020) 121703] proposed Modified Maxwell (ModMax) model of nonlinear duality-invariant conformal electrodynamics. Here, Generalized ModMax (GenModMax) model of nonlinear electrodynamics coupled to general relativity is studied. The metric and mass functions and their asymptotic as [Formula: see text] and [Formula: see text] of a magnetic black hole are obtained. Corrections to the Reissner–Nordström solution are found and we show that for some model parameters the black hole is regular. The Hawking temperature and heat capacity of black holes are calculated and phase transitions are investigated. We demonstrate that black holes are not stable for certain model parameters.

On generic rotating regular black hole solutions

In the present paper, we study rotating regular black hole (RBH) in the model of nonlinear electrodynamics (NED) in the framework of General Relativity (GR). The paper explores derivation of the generic form of rotating RBH solutions which can be written in Kerr-like form in Boyer–Lindquist coordinates. It is shown that RBH solutions depend on NED Lagrangian. Lastly, we also showed that Kerr–Newman–Taub–NUT spacetime, which is solution of Einstein–Maxwell equations, can be a candidate for one of exact analytical rotating RBH solution by calculating curvature invariants at origin r=0, as well as, Kerr–Taub–NUT and Taub–NUT spacetimes.